After restructuring your website, give a permanent redirect in .htaccess file to intelligently redirect users as well as Search Engines. Specify your preferred version – printer or robot.txt file and www or non-www (if you have link on other sites, then specifically mention how do you want your URL to be indexed links with www or links without www) for indexing, instead of webmasters taking a decision on the best version, also specify how your website should be taken into account using www or non-www version.
Despite including lengthy copyright text on the bottom of every page, write a very brief summary and link it to a page with complete details. Use Top Level Domains whenever and wherever possible to manage country specific content, to let webmasters serve the most appropriate version of a document. Make sure you're accustomed with how content is showcased on your site, especially if it includes a blog, a forum, or related system that often shows the same content in multiple formats. For any other issue regarding duplicate content you can file a DMCA request to claim ownership of the content and have webmasters deal with the rogue site.
In short, a general awareness of duplicate content issues and a few minutes of thoughtful preventative maintenance should help you to help webmasters provide users with distinct and Relevant Website Content.
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